ADSL Connection keeps terminating

Hello there, im gonna bore you all with another of my problems.

I'm currently connected to the internet with an Alcatel Speedtouch 330 USB ADSL modem on the ISP Zen Internet.
Problem is, randomly across the day (could be every 5 mins, or 3 hours) my connection gets terminated.

I open up the dialer again and get 'no dial tone'.
I keep trying to redial about 10 times until it decides to connect.

I commonly use Mozilla firefox, WS_FTP and my computer is protected by norton anivirus, symantech personal firewall & adaware.

I've tried everything to sort this out, here are my recommended solutions which didnt work:

Check the phone line (dial tone fine)

Try the modem on another PC (works well)

Change the USB power management so that the system doesnt turn them off to save power (done, still keep disconnecting)

Check for spyware & internet dialers (downloaded adaware, 50 critical files found, 10 of those internet dialers, still keep disconnecting)

Download updated modem driver (nope, doesnt change a thing)

Check for viruses (not tried that yet, but i doubt there's any there)

Tried different USB ports (yup, nothing happens)

Being a web-designer & surfer, this hinders my work greatly, please help!

I actually got disconnected 3 times while typing this message!!!

Try reinstalling the drivers for ur modem. Uninstall the original ones first then the new one.

If the doesnt wrk ring up your ISP and abuse them.

yeah, ill have a go at that again.

Thanx kiwi, you're about the only person on the internet who's replied when i needed support.

tried reinstalling and it didnt work. I emailed the ISP and he said there might be a fault on my system.

Damn i hope not, i've wiped the hd god knows how many times this year.